Short wave aerial



Nov. 3, 1931. F. SCH-RGTER 1,830,176

SHORT WAVE AERIAL Filed Oct. 27, 1927 INVENTOR FRlTZ SCHROETER Adam A ORNEY in the plane of Patented Nov. 3, 1931 UNITED STATES PA ENTsoaring;

ERrrz scHRti'rER, or BERLIN, GERMANY, AssrGNoR roGEsEL soHAE'r Et'rR mam- LOSE TELEGRAPHIE M. B. 1-1., or BERLIN, GERMANY, A CORPORATION or GERMANY SHORT WAVE AERIAL Application filed October 27, 1927, Serial No.

In the transmission of intelligence on short waves, trouble arises quite frequently in so far as doubling of the transmitted signals occurs; indeed, it has been possible to ascertain that such double signals are due to the fact the oscillations sent out are received at the incoming antenna over two or more paths of different lengths. The case that has been observed most frequently is that in which the waves radiated off by the transmitter do not only come from the direction of least distance between sending and receiving points, but also from the opposite direction. That is if the propagation of the waves is examined the large circle obtained by the intersection of the earths surface and a vertical plane passed or laid through the sending and receiving points, it will be found that the incoming signals reach the receiving station in both directions around the earths sphere.

On basis of the difference of times of arrival of the same signals via these two routes, it has been found that the propogation of the waves, ner as above suggested. It therefore follows that the receiving apparatus will record the same signal twice with a time difli'erence equalling the difference in distance or path, with the result that the reception of the incoming signals is disturbed.

The object of thisinvention is to provide means to eliminate the undesired signals.

Now, to eliminate this source of trouble in reception, according to the disclosure of the present invention, a screening or shielding device is provided adapted to preclude the waves from the receiving aerial coming from the disturbing direction. This screening or shielding arrangement whereby the present trouble is entirely prevented consists in that in the rear of the receiving antenna, i. e., in the direction away from, or remotest from, the sending station, an electrical screen comprising a row of wires suspended vertically in an insulated manner is disposed, the length of all of these wires to be larger than the length of. the antenna. The antenna is united with the receiving apparatus by a so-called as a matter of fact, occurs in a man 228,986, and in- Germany December 8, 1926.

energy (transfer) line consisting of a parallel wire system.

Another object of the invention is to provide apparatus simple in structure and adapted to be readily installed.

Other objects and advantages will become apparent from the following specification when read in connection with the accomp anying drawing in which the single figure shows diagrammatically the present preferred form of my invention.

Referring to the drawing the receiving antenna consists of a dipole antenna A which is joined to the receiver apparatus E by means of a parallel-wire system 70. The waves come in from a direction indicated by the arrows. Upon the other side turned away from the receiving direction is mounted a screen B. On three poles or masts M1, M2, M3, which are suitably so mounted that the two lines of junction form an acute angle between each other, there isstretched a cable or rope s, and suspended in vertical direction from insulators i are conducting wires. The figure also indicates the sizes or dimensions whereby complete screening of disturbing waves arriving from rearward direction is possible. It will be noted that the vertical wires suspended in the middle are of greater length than those at the two ends of the screen. The distance from the aerial A of the screening wires is suitably fixed at threequarter wave-length or another odd multiple of a quarter-wave.

Having now described my invention and the operation thereof I claim:

1. The combination with a receiving antenna of an untuned conductive screen located on the side of the antenna awa from a desired transmitting station, in order to screen the antenna from. radiation approaching from the opposite direction around the earth said conductive screen comprising a plurality of parallel conductors of graduated and untuned lengths.

2. The combination with an antenna of an essentially aperiodic conductive screen located on the side of the antenna away from a desired transmitting station, in order tc screen the antenna f1 om signals approaching from the opposite direction said conductive screen comprising a plurality of parallel conductors of different untuned lengths.

3. The combination with a short Wave receiving antenna of a screen comprising a plurality of verticalnconductorsof. graduatedanduntunedllengths situated on the side of the antenna away from a desired transmitting station.

FRITZ sGHRoTER; 

